1. Field of the Invention
The present invention relates to a printing apparatus which performs printing by applying ink from a print head to a sheet.
2. Description of the Related Art
Head temperature of an inkjet printing print head increases in continuous use. The discharge characteristics of ink from a nozzle vary as the temperature increases. In serial printing where a print head is reciprocated to form an image, changes of the head temperature during printing are a degrading factor of image quality since there can be portions of different hues and/or densities in an image.
An apparatus discussed in Japanese Patent Application Laid-Open No. 2009-012462 detects a temperature of a print head. According to the detected temperature, the apparatus sets the number of scans in which waiting is performed, and a wait time between a head scan and the next head scan.
According to Japanese Patent Application Laid-Open No. 2009-012462, wait times are distributed among a plurality of scans so that each single wait time does not become long in order to suppress hue and density unevenness in a formed image. However, depending on the duty of an image to print, the head temperature can rise or fall sharply during printing of a single scan.
In such a case, subsequent wait time needs to be re-set. If the wait time before and after re-setting is greatly different, the permeability of ink to a sheet can vary in that area. Accordingly, there still remains the possibility of causing large unevenness in hue and/or density.